The present invention relates to a method for the treatment of liquid dross and waste metal obtained in smelting and remelting plants and which is poured from the melting furnace into a skimming trough whereupon the dross is conveyed from the trough into a rotating, substantially horizontal cooling pipe in which it passes from one end to the other thereby becoming cooled below the melting point to obtain a granulated form. The invention further relates to apparatus for carrying out the method.
It is well known that waste metal and liquid dross obtained in the smelting and remelting of metal generally contain a substantial percentage of pure metal. For this reason, it is common practice for such waste metal and liquid dross to be collected and conveyed to separate recovery plants. According to the arrangement illustrated in German Offenlegungsschrift No. 27 13 281, which concerns the recovery of aluminum for aluminum dross, the hot aluminum dross is charged into a rotating open cooling drum in which it is cooled. The cooling and circulation of the dross in an open drum will of course result in oxidation of at least a portion of the aluminum due to contact with air. This results on the one hand in an increase in the temperature of the dross which must of course be compensated for through increased cooling action and on the other hand a decreased yield in the amount of pure aluminum recovered. Since aluminum oxide has a lower market value than pure aluminum, the economy of the procedure is not as high as is desired.